Interacting with Shadow

I spied my shadow slinking
Up behind me in the night,
I issued it a challenge,
And we started in to fight.
I wrestled with that shadow,
But it wasn't any fun,
I tried my very hardest --

All the same, my shadow won.

—"I Spied My Shadow Slinking", from The New Kid On The Block by Jack Prelutsky

An occurrence in most forms of media, where a character who is usually a Cloudcuckoolander or a Dojikko, will very often talk with his shadow like it's a real person.

Compare: Imaginary Friend, Consulting Mister Puppet, Not-So-Imaginary Friend

Contrast: Living Shadow, in which the shadow really is a living being.

Examples of Interacting with Shadow include:

Anime and Manga

In Soul Eater Chrona does this inside their mind. It asks him several would-be Armour Piercing Questions, but the only answer Chrona gives it is "pass".
Blue Dragon: this is pretty much the story.
Gekko Moria from One Piece ate the Shadow Shadow Fruit (Kage Kage no mi), allowing him to manipulate shadows. Amongst various tricks he can remove the shadows of people, make pacts with them and put them in another body (dead or living). Though shadows can't talk, they're shown understanding Moria's words.

Comic Books

In Emily The Strange: When your shadow starts a fight... ...turn out the light.

Film

Sinister example from The Princess and the Frog: Dr. Facilier, the aptly named Shadow Man often interacts with his shadow.
In Peter Pan when Peter first meets Wendy his shadow has been ripped off his body, and Wendy sews it back on (it attaches at the feet).
Who Framed Roger Rabbit?: While Eddie Valiant is in Toontown tracking the murderer of R. K. Maroon, he walks down an alley with his shadow appearing on the wall. He sneezes and his shadow turns to him and says "Gesundheit", to which Eddie replies "Thank you".
In Hook, Peter's shadow points him to his old house in the hollow tree.
In The Great Muppet Caper, during the "Steppin' Out with a Star" musical number, Kermit's shadow briefly starts dancing on its own.

Literature

The poem, I Spied My Shadow Slinking, by Jack Prelutsky.

Music

The song, "Me And My Shadow", possibly the Trope Codifier.

Web Comics

The first page of Gunnerkrigg Court ends with Annie explaining she's obtained a second shadow (which turns out to be one of a race of Living Shadows). Subsequent pages have her manage to establish communication with it.
Sluggy Freelance: Bun Bun was, for a time, cursed with the shadow of the Groundhog. It annoyed him nearly to death.

Western Animation

An episode of The New Adventures of Winnie the Pooh had Piglet befriend his shadow, when his friends were too busy with their own activities to play with him.
At the beginning of |Jack Frost, Pardon-Me Pete the groundhog is briefly seen interacting with his shadow.
Rocky and Bullwinkle: One of the Aesop and Son segments features interactive shadows.
In the intro of the Lucky Luke cartoon, we see the title character actually shooting his shadow in a duel.